1. Field of the Invention
The present invention relates to an optical spectrum analyzer using a waveguide acousto-optic tunable filter.
2. Description of the Related Art
In order to measure a light output in a wavelength range of light to be measured, various optical spectrum analyzers have been disclosed. For example, Japanese Unexamined Patent Application Publication No. 2002-214459 discloses an optical spectrum analyzer including a tunable filter using an arrayed waveguide grating. Here, by using the arrayed waveguide grating, light having a target wavelength is extracted. Japanese Unexamined Patent Application Publication No. 2002-214459 also discloses that, by thermo-regulating the arrayed waveguide grating, a target wavelength can be changed.
Further, Japanese Unexamined Patent Application Publication No. 2001-264167 discloses an optical spectrum analyzer using a tunable fiber grating. By using the tunable fiber grating, light having a target wavelength is extracted. Here, the optical spectrum analyzer is configured so that, by extending or contracting the fiber grating using a piezoelectric element, a target wavelength can be changed.
In an optical analyzer using an arrayed waveguide grating, by using a Peltier element, a heater, or other suitable device to perform thermo-regulation, a wavelength is changed. Accordingly, the spectrum analyzer does not include any mechanical driving parts, but takes a relatively long time for its temperature to change. Thus, this optical spectrum analyzer is unsuitable for high speed measurement.
On the other hand, the optical spectrum analyzer, using the wavelength variable fiber grating, as described in Japanese Unexamined Patent Application Publication No. 2001-264167, is relatively small because it uses a piezoelectric element, and can perform measurements at a relatively high speed. However, it has a problem of a narrow tunable range.